Adding toggle switch to 8200R

I was watching a YouTube video where the builder added a toggle switch to the 8200dx for the triode and ul setting. Is this possible with the 8200r? The layout is different . Where would one attach the switch wire. On the 8200dx, it is connected to a resistor, but on the 8200r there is a ptc thermistor in its location. Any suggestions?
 
What number is full dc voltage ? The switch I have is 3A-250V;5A-125V; Does this cover your suggestion? I'm in the U.S. is it dangerous even if the switch is wired correctly? Duly noted about switching while powered off. thanks for your suggestions.